An interconnect pump station for the Castle Pines North Metro District isunder construction.

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Manouch Afshar, visiting his Arabian stallion Roshan at his home on Mountain View Lane in Douglas County, says "a huge amount of water" is needed to care for his family's six horses. With increasing water prices and plans for a new large development nearby, Afshar is thinking about looking for a hydrant and hauling in water, just as he did several years ago. story, 17A

Twenty-five utilities between Denver and Colorado Springs are together pumping 38,742 acre-feet of water from 449 municipal wells each year, according to data provided by the water suppliers. That works out to about 400 gallons per second being squeezed from the Denver Basin aquifer.

It’s not that the water in the vast aquifer is expected to run dry anytime soon. The problem is that pumping water from as deep as 2,200 feet below the surface is getting more difficult — and expensive.

This is driving the hunt for renewable surface water, drawn from streams and rivers, the rights to which are nearly all claimed.

“They’re all trying to shift, but it’s going to be years,” said Scott Orr, pump division manager for well company Hydro Resources Inc. “Where are they going to get the surface water? And where are they going to get the infrastructure to move it? You’re talking millions and millions just for the water rights. That doesn’t get you the pumps, pipelines, water-treatment stuff. I don’t think I’m going out of business anytime soon.”

Colorado embraced groundwater in the wake of some of the nation’s fastest suburban expansion around 1993, when plans for the Two Forks dam — designed to supply Front Range communities for decades — were rejected.

Developers pressed ahead, tapping aquifers to serve new homes.

Colorado law allows anyone who owns land over the Denver Basin — stretching from Greeley to Colorado Springs and from the foothills to Limon — to draw the water below.

The result today is that “there’s a significant portion of the state’s economy built on this groundwater,” said Rod Kuharich, director of the South Metro Water Supply Authority, which represents 15 suburbs.

But the aquifers are finite.

“We’re getting people calling in asking, ‘Are we going to run out of water?’ ” Colorado Geological Survey director Vince Matthews said.

The water table and well-production data kept by some utilities show well levels falling by as much as 30 feet a year and that well flows in summer slow by as much as 20 percent.

State officials say it would be prudent to drill monitoring wells to track changes in aquifers. Assistant state engineer Kevin Rein said he hears “horror stories of water levels dropping and water becoming more expensive to pump.”

When Two Forks was rejected, “the consensus was that groundwater was a very viable source that could be replenished,” said Jim Sherer, the Environmental Protection Agency’s regional administrator at the time, who favored the dam. “You could put water back in. What seemed to be easy answers 20 years ago is creating problems today.”

The prime alternative for some suburbs today involves diverting wastewater from Denver and Aurora and purifying it for use by others.

Over the past year, 15 south metro suburbs have been been negotiating the Water Infrastructure and Supply Efficiency, or WISE, project.

It would take advantage of Aurora’s new $660 million Peter D. Binney treatment plant, combined with the city’s 34-mile pipeline that diverts water from the South Platte River, downstream from Denver’s Metro Wastewater Reclamation facility.

Aurora’s plant can purify 50 million gallons of wastewater a day. The end product, operators say, meets federal drinking water standards.

“As long as there’s adequate monitoring, people should not have to worry,” said Suzanne Paschke, a U.S. Geological Survey groundwater hydrologist and geochemist. “Treatment technologies have improved.”

Yet-to-be-built pipelines would connect Aurora’s plant with metro suburbs as far south as Castle Rock.

“What we’d do is give water to people who need it most of the years,” said Denver Water planning director Dave Little. “If we need it during dry times, we’d take it back. It works to try to get them weaned off wells.”

Denver would gain a pipeline link so that treated wastewater could augment Denver’s current surface water supplies. Aurora would gain revenue to pay down debt on its water plant. Suburbs initially could receive 10,000 acre-feet of purified wastewater, Little said.

But Denver’s participation depends on diverting more water from the west side of the Continental Divide, he said. The proposed Moffat Tunnel diversion project is under review.

“The more water we bring over from the Western Slope, the more return flows (to the South Platte) we have,” Little said. “If we didn’t get the Moffat project, it could limit our ability to fully participate in the WISE project. I don’t think it would kill it.”

Suburban leaders are counting on WISE. They anticipate receiving as much as 60,000 acre-feet of wastewater annually for reuse, said Pat Mul hern, who manages the Cottonwood, Inverness and Stonegate water districts.

The cost has not been calculated.

A South Metro Water Supply Authority study found that the cost of shifting 11 suburbs from wells to surface water probably will range between $2.2 billion and $4 billion.

For now, the total amount of water pumped from aquifers is increasing.

In the Denver metro area, the Arapahoe County Water and Wastewater Authority pumped 3,097 acre-feet last year, up 84 percent from 1,687 acre-feet in 1998. Groundwater pumped at the Pinery, where two new wells are planned, increased 65 percent since 2005.

Federal agencies do not collect data from water providers but have used projections to estimate the impact of Colorado’s groundwater pumping.

An unpublished USGS study found that total water pumped from the entire Denver Basin topped 80,300 acre-feet in 2003, up from 58,641 in 1996.

The amount of water pumped is increasing by 3,102 acre-feet per year, USGS hydrologist Paschke concluded. “The rate of pumping is exceeding the rate of replenishment,” she said.

Suburbs also are scrambling on their own to try to line up renewable surface water supplies.

East Cherry Creek Valley, with 85 wells, has installed a pipeline to bring water bought from farmers.

This month, Castle Rock will drill shallow wells along Plum Creek, tapping a surface source. Currently, residents depend on 52 municipal wells that pumped 7,200 acre-feet of water last year, up from 5,900 in 2009.

Each summer, well production drops 10 to 20 percent, Castle Rock water engineer Heather Beasley said. “If you’re sucking water out of a sponge through a straw, it takes time for the water at the edge of the sponge to reach the center.”

Similarly, Castle Pines North water providers are building a pump station and pipeline to move treated wastewater from Highlands Ranch.

“It’s the right thing to do,” Castle Pines North manager Jim Worley said. “Groundwater can run out. Surface water is renewable.”

The Centennial Water and Sanitation District, which supplies Highlands Ranch, pumps an average of 1,500 acre-feet a year from 54 wells, district manager John Hendrick said.

Worried about the wells, the district bought shares in a ditch company northeast of Denver and had the agricultural water rights converted in state court to municipal rights.

Some years now, Centennial barely has to pump groundwater at all and also can reinject surplus water into the aquifers through two-way valves.

“We’ve learned a lot about aquifers over the years,” Hendrick said. But the rising cost of continuing to rely on wells “is something people didn’t really look at” when Colorado turned to groundwater to enable growth.

Bruce Finley covers environment issues, the land air and water struggles shaping Colorado and the West. Finley grew up in Colorado, graduated from Stanford, then earned masters degrees in international relations as a Fulbright scholar in Britain and in journalism at Northwestern. He is also a lawyer and previously handled international news with on-site reporting in 40 countries.